The following account of the prior art relates to one of the areas of application of the present invention, namely in connection with hearing aid instruments with a behind the ear part comprising an exchangeable battery.
US publication No 2007/0081684 relates to a hearing aid with a battery compartment having a battery lid or battery access door which is hingedly connected to the casing to allow pivotal motion between the battery door and the casing, where a flexible latch having a proximal end and a distal end is provided at the battery door, where the distal end of the flexible locking latch is arranged to flex along a path in order to release the battery door and wherein an arrest pin is insertable in the moving path of the distal part of the flexible locking latch to block the movement of the latch when a child-resistant battery enclosure is desired. This example of prior art suffers from the problem that the locking pin ads un-necessary complexity to the construction and that it may also accidentally fall out and thus the effect of childproofing is gone.
Further, from EP 0674465 a hearing aid with childproofing of the battery door is known, where the door may be opened by the insertion of a screwdriver or the like into a small aperture between battery door and the hearing aid shell. The aperture is provided behind a protrusion which prevents a child from reaching into the aperture. The problem with this prior art child proofing is that the protrusion leaves plenty of possibility for the child to open the battery door using mouth and teeth, and a reliable security against attempts to open the battery door is not achieved. Also the protrusion is cosmetically unattractive and therefore undesirable.